Habitat use and trophic structure in a microbat assemblage on the edge of the southern rangelands, Western Australia: insights from stable isotope analysis

Abstract

The microbat assemblage on Charles Darwin Reserve was investigated between 2007 and 2009 to provide a benchmark for monitoring long-term responses to climate change on a major bioregional boundary, the mulga–eucalypt line. Stable isotope analysis of bat fur was used to interpret the current local habitat and trophic relationships between microbat species with different biogeographical affinities. The stable isotope values of the ants inhabiting 10 broad vegetation types were used to provide an isotopic baseline of the Reserve to assist in the interpretation of the δC or δN signatures observed in the bat assemblage. The δC signatures of ants in both a Salmon Gum woodland and an arid shrubland shifted significantly after the breaking of a prolonged drought but there was no change in the bats. The ubiquitous bat species, and those with south-western affinities, probably used most of the available vegetation types on the Reserve and displayed some significant differences in mean trophic level. Scotorepens balstoni, a species of the southern interior of Western Australia, specialised at foraging within patches of eucalypt woodland. Vespadelus baverstocki, a southern arid zone species, was evidently restricted to the proximal arid habitats with distinctively high δN signatures.